I seriously doubt there's very much highly relevant old knowledge locked away somewhere. Is there interesting stuff we don't have good access to? Sure, but mainly of interest to historians (pro or amateur). You're not likely to find the cure for cancer written down in some 1000-year-old book somewhere. And while a few people might really be interested in reading decades or centuries-old novels that weren't popular enough to be called "classics" now, the vast majority of people aren't going to find such stories about people in the distant past all that interesting.
Of course, it's best to preserve past knowledge, but I think the idea that this is part of some kind of conspiracy to keep people buying new stuff is pretty silly. People are always going to want new stuff, as society grows and changes.
Of course, it's best to preserve past knowledge, but I think the idea that this is part of some kind of conspiracy to keep people buying new stuff is pretty silly. People are always going to want new stuff, as society grows and changes.